The present invention relates to a headphone preferably comprising a toroidal seal ring which, in operational position, rests against or surrounds the user's ear and is made of a soft, yielding, preferably elastic material, and by which, with the headphone put on, a coupling space between the diaphragm, actuated by an electroacoustic transducer, and the auditory canal is formed and largely sealed off to the outside.
It is well known that the manner of coupling of the headphone or the transducer diaphragm comprised therein to the ear is of fundamental importance for the acoustic impression.
An impression closer to natural sound perception is obtained by providing that the headphone is not brought into tight contact with the ear but put on with the interposition of a foam material pad. A headphone of such a design is termed an "open headphone". The manner of coupling used in this case, however, has the disadvantage that, due to the sound path from the front to the backside of the transducer diaphragm acting as an acoustic short, the reproduction of the low frequencies is deficient. This results from the fact that the foam pad represents a frictional resistance having only a small acoustic mass, to which the acoustic frictional resistance provided for the damping of the diaphragm and, if provided, an acoustic mass coupled with the transducer diaphragm, are to be added. Thus, in a known headphone of this kind, only frictional resistances and acoustic masses are located in the sound path from the front to the back side of the transducer diaphragm and that is why its response, which is a function of the reciprocal ratio of the wave length to the length of the sound path around the transducer diaphragm, is dependent on frequency. This accounts for the decline at the low end of the frequency characteristic in the so-called open headphones.
In the other type of headphones in which an as close a coupling as possible between the transducer diaphragm and the ear is sought and the tight enclosure at the ear is realized by means of a soft ear cushion, not only the wellknown and unpleasant "in-the-head-localization" of the transmitted acoustic event occurs but, in addition, the frequency range from about 200 Hz to about 1500 Hz is over-accentuated.